我在iOS应用中使用了以下NSFetchedResultsController：
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:@"ToDoItems" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
NSSortDescriptor *sort = [[NSSortDescriptor alloc]
initWithKey:@"tdText" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];
[fetchRequest setFetchBatchSize:20];
NSFetchedResultsController *theFetchedResultsController =
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil
cacheName:@"Root"];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;
return _fetchedResultsController;
}
要测试它我使用以下代码：
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
int numero = [self.fetchedResultsController.fetchedObjects count];
NSLog(@"Numero=",numero);
switch (section)
{
case 2 : return numero;
case 3 : return 30;
default : return 8;
}
}
我确定，实体ToDoItems现在有1个对象（使用SQLite Manager检查），但NSLog显示Numero=
我的代码出了什么问题？
答案 0 :(得分：2)
首先你的日志不正确，正如我在评论中所说的那样。
NSLog(@"numero = %d", numero);
然后你应该正确实现表视图的数据源方法。 e.g。
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return [[fetchedResultsController sections] count];
}
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section {
id sectionInfo =
[[fetchedResultsController sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
}
numero这里是[sectionInfo numberOfObjects]。
有关详细信息，请查看NSFetchedResultsController tut，以及“核心数据编程指南”。这是你的参考手册。
答案 1 :(得分：1)
您实际上并未打印出NSLog语句中的数字
使用
NSLog(@"Numero=%d", numero)
答案 2 :(得分：0)
我不确定我是否完全理解你想要实现的目标，但如果你想要一个带有固定部分的UITableView和一些从Core Data填充的部分和其他硬编码的部分，也许就像侧边栏菜单一样，那么你需要做类似于以下。请注意，在下面的示例中，“任务和可交付成果”部分中的项目是使用fetchedResultsController从Core Data获取的（但是只需正常的提取就可以了，但我太懒了，无法删除fetchedResultsController代码！）。我所做的只是得到一个结果数组，所以我不使用任何委托方法。
这些部分在sectionsArray中定义，每个部分的项目都包含在单独的数组中，并存储在名为sectionMenus的字典中。
另请注意，当从Core Data加载数据时，我加载了一个临时菜单项（“正在加载，请稍候......”）（iCloud文件可能尚未下载数据）。
无论如何，请查看此链接中的视频，了解应用运行时此“菜单”的外观。
http://ossh.com.au/design-and-technology/software-development/uimanageddocument-icloud-integration/
在tableViewController .h文件中添加sectionMenus字典和sectionsArray数组，如下所示
@interface MenuViewController : BaseMenuViewController <NSFetchedResultsControllerDelegate> {
NSArray *sectionsArray;
NSMutableDictionary *sectionMenus;
bool _isLoaded;
}
@property (strong, nonatomic) NSFetchedResultsController *fetchedResultsController;
@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (strong, nonatomic) NSString *entityName;
@end
现在在.m文件中，您需要执行以下操作：
#define MENU_PROJECT @"Project"
#define MENU_TASKS @"Tasks and Deliverables"
#define MENU_FINANCE @"Finance"
#define MENU_QUALITY @"Quality"
#define MENU_IT_SYSTEMS @"IT Systems"
#define MENU_ADMIN @"Administration"
#define SUBMENU_SCOPE @"Scope"
#define SUBMENU_LOADING @"Loading, please wait..."
@implementation MenuViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//[self.openingViewController setFilesName:self.filesName];
//[self.openingViewController setFilesDate:self.filesDate];
// If we get menu's from the database set this to YES
_isLoaded = NO;
sectionMenus = [[NSMutableDictionary alloc] init];
sectionsArray = [[NSArray alloc] initWithObjects:MENU_PROJECT, MENU_TASKS, MENU_FINANCE, MENU_QUALITY, MENU_IT_SYSTEMS, MENU_ADMIN, nil];
NSString * bundleID = [[NSBundle mainBundle] bundleIdentifier];
if ([bundleID isEqualToString:@"au.com.ossh.iProject2FreeiPad"])
{
[sectionMenus setObject:[[NSArray alloc] initWithObjects:SUBMENU_SCOPE, nil] forKey:MENU_PROJECT];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:SUBMENU_LOADING, nil] forKey:MENU_TASKS];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:@"Expenses", nil] forKey:MENU_FINANCE];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:@"Issues", nil] forKey:MENU_QUALITY];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:@"Applications", nil] forKey:MENU_IT_SYSTEMS];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:@"People", nil] forKey:MENU_ADMIN];
} else {
[sectionMenus setObject:[[NSArray alloc] initWithObjects:SUBMENU_SCOPE, nil] forKey:MENU_PROJECT];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:SUBMENU_LOADING, nil] forKey:MENU_TASKS];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:@"Expenses", @"Ongoing Costs", @"Timesheets", nil] forKey:MENU_FINANCE];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:@"Issues", @"Risks", nil] forKey:MENU_QUALITY];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:@"Applications", @"Interfaces", nil] forKey:MENU_IT_SYSTEMS];
[sectionMenus setObject:[[NSArray alloc] initWithObjects:@"People", @"Setup", nil] forKey:MENU_ADMIN];
}
// Do any additional setup after loading the view.
self.entityName = @"ProjectCategory";
[self fetchedResultsController];
}
- (void)reload {
NSArray *tadMenus = [self projectCategories];
if (tadMenus) {
_isLoaded = YES;
[sectionMenus setObject:[[NSArray alloc] initWithArray:[self projectCategories]] forKey:MENU_TASKS];
} else {
_isLoaded = NO;
}
}
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[self.tableView reloadData];
}
// Override this to set your own.
- (NSArray*)sortDescriptors
{
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"sortIndex" ascending:YES];
NSArray *sortDescriptors = @[sortDescriptor];
return sortDescriptors;
}
#pragma mark - Fetched results controller
- (NSFetchedResultsController *)fetchedResultsController
{
/*
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
*/
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:self.entityName inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
//[fetchRequest setFetchBatchSize:20];
[fetchRequest setSortDescriptors:[self sortDescriptors]];
// Edit the section name key path and cache name if appropriate.
// nil for section name key path means "no sections".
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
aFetchedResultsController.delegate = self;
_fetchedResultsController = aFetchedResultsController;
NSError *error = nil;
if (![_fetchedResultsController performFetch:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return _fetchedResultsController;
}
- (NSArray*)projectCategories {
//LOG(@"projectCategories called");
int count=0;
id <NSFetchedResultsSectionInfo> sectionInfo;
if ([[[self fetchedResultsController] sections] count] > 0) {
sectionInfo = [[[self fetchedResultsController] sections] objectAtIndex:0];
count = [sectionInfo numberOfObjects];
} else
count = 0;
//FLOG(@" %d categories found", count);
if (count == 0) return nil;
NSMutableArray *projectCategories = [[NSMutableArray alloc] initWithCapacity:count];
for (NSManagedObject *item in _fetchedResultsController.fetchedObjects)
{
[projectCategories addObject:item];
//FLOG(@" adding category %@", [item valueForKey:@"name"]);
}
return projectCategories;
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return [sectionsArray count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [[sectionMenus objectForKey:[sectionsArray objectAtIndex:section]] count];
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
return [[sectionsArray objectAtIndex:section] description];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *simpleTableIdentifier = @"SimpleTableItem";
static NSString *inactiveTableIdentifier = @"InactiveTableItem";
UITableViewCell *cell;
NSObject *menuItem = [[sectionMenus objectForKey:[sectionsArray objectAtIndex:[indexPath section]]] objectAtIndex:[indexPath row]];
NSString *menu = [menuItem description];
cell.textLabel.text = menu;
return cell;
}